Student Project Abstracts 2005 - Pluto - University of Washington

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BUILDING AN OPTICAL OXIMETER TO MEASURE THE OXYGEN CONTENT OF BLOOD NON-INVASIVELYA 1/8” diameter optical fiber collects and directs light to thePMT. Voltage controlled crystal oscillators (VCXO) are usedto provide the AC signal and a laser current supply is used toSignalprovide the DC power. Photomultiplier The laser diode is poweredInputto its Lock-In lasingTube (PMT)Amplifierthreshold, so that the AC signal appears as a change in intensity.Changes in the oxygenation levels of the blood are expected toVoltage Controlledcorrespond with changes Crystal in the Oscillator signal amplitude. A phase lockedloop (PLL) locks the phase between the VCXO signals whichprevents drift in the frequency. Frequency mixers Input output 1 the differencebetween two input frequencies (figure 2).Oximeter probe (heldin place by elasticband)The laser light is intensity modulated to allow the measurementof intensity Optical fiber as well asLaserphasediodeshift. From this informationthe absorption and scattering may be determined (Hueber et al.,2001). TypicallyTargetfrequenciesarea – dashed linearound 100 MHz or higher haverepresents average path ofbeen used in other oximetersphotons(Franceschini et al., 2002; Ma etDC Biasal., 1999). The modulation for the oximeter was chosen to be54 MHz because the laser diodes had higher intensities at thisThe laser light is intensity modulated to allow the al., 1999).frequency than at the other frequency choice of 100 MHz (figureFigure 2. Diagram of one channel of the oximeter. 45 mA is used for the DC bias. Circles represent the frequency mixers.measurement of intensity as well as phase shift.From this information the absorption and scattering4). The setup figure 3 was used to test the frequency rangemay be determined (Hueber et al., 2001). Typicallyavailable.frequencies around 100 MHz or higher have been usedin other oximeters (Franceschini et al., 2002; Ma etPhase Locked LoopVoltage ControlledCrystal OscillatorReferenceout: 1 kHzInput 2Control voltageThe modulation for the oximeter waschosen to be 54 MHz because the laser diodes hadhigher intensities at this frequency than at the otherfrequency choice of 100 MHz (figure 4). The setup infigure 3 was used to test the frequency rangeavailable.OscilloscopeCh2 Ch1PMTSignalGeneratorFigure 3. Setup for the test of thelaser diode and PMT signal. Theoscilloscope (Tektronix model TDS3054) is set to acquire at 64averages.Figure 4. Frequency range test for the red and near infrared laserLaserFigure 4. Frequency Near range infrareddiodes. test for laserThediodeSupplyamplitude of the signal from the PMT is greater aroundthe red and near infrared laserdiodes. The amplitude % PMT of the Amp 50 signal MHz vs. Freque than at 100 MHz. In the oximeter, the light collected will befrom the PMT is greater around 50 MHz than at 100 MHz. In the oximeter, the light collected will be a small fractionFigure 3. Setup for the test of the laser diode and PMT signal. Thea small of the2.5fraction of the light emitted by the laser diode sources, so it islight emitted by the laser diode sources, so it is important that the laser diodes emit at as high an intensity as practical.oscilloscope (Tektronix model TDS 3054) is set to acquire at 64 averages.important that the laser diodes emit at as high an intensity as practical.2.0Experimenttissue in preliminary testing (figure 5). A 1/4” holeA white phantom was used to simulate biological1.5in the phantom allows a cylinder of black plastic orred plastic to be inserted. 1.0 The black plastic isEXPERIMENT expected to absorb light and the red plastic is expected1-2 cmto reflect red light. The 0.5 red laser diode was used inSource (laserDetector (opticaldiode, 635 nm)fiber to PMT)0.0A white phantom was used to simulate biological tissue in10 20 30 40 50 60 70 80 90 100preliminary testing (figure 5). A 1/4” hole in the phantom allowsa cylinder of black plastic or red plastic to be inserted. The blackPhantomplastic is expected to absorb light and the red plastic is expected toreflect red light. The red laser diode was used in the test. The signalwas collected through a BNC board using the NI-DAQ systemwith LabView 6.0. The oximeter was tested with a source-detectorseparation of 1 cm (figure 6) and 2 cm (figure 7).Frequency (MHPMT Amp/Ref Amp (%)Figure 5. Phantom test for the oximeter. The phantom is placed so the holeis equidistant from the centers of the source and detector. The dashed linerepresents the average path traveled by photons collected by the detector.Figure 6. Oximeter tested using the red laser source (635 nm) with 1 cmbetween the source and detector. Left: Signal amplitude when the redand black plastic are alternated. Right: Signal amplitude with only thered or black plastic in the phantom. The amplitude for the red plasticis larger relative to the amplitude for the black plastic. Differences inthe red/black values between tests are most likely due to irregularitiesin the testing procedure (e.g. phantom was not well secured).72 CMDITR Review of Undergraduate Research Vol. 2 No. 1 Summer 2005
LINACKNOWLEDGEMENTSThis research funded by the National Science FoundationSTC-MDITR and Research Experiences for Undergraduates program.Dr. Antao Chen of the Applied Physics Laboratory at theUniversity of Washington mentored the research.JoAnn Lin plans to continue research work and is currently pursuing abachelor’s degree in Bioengineering at the University of Washington.Figure 7. Oximeter tested using the red laser source (635 nm) with 2cm between the source and detector. Left: Red and black plastic arealternated. Right: Only the red or black plastic in the phantom. Theamplitude for the red plastic is larger relative to the amplitude for theblack plastic. Differences in the red/black values between tests are mostlikely due to irregularities in the testing procedure. At 2 cm separation,the light collected by the PMT is more scattered and has lower intensitythan at 1 cm. The noise in the signal is significant at 2 cm separation.FUTURE WORKOne channel of the oximeter was successfully built. Testingis ongoing, and will include the phantom test with the nearinfrared laser diode and a greater variation of source-detectorseparation. The spacing of the optical fiber and laser diode onthe oximeter probe will be adjusted according to the values formaximum and optimum source-detector separation.Future work includes building another channel for the secondlaser diode and reducing noise in the signal. The oximetermust also be made more compact for practical use. In the futurethe oximeter may be tested on live subjects (pending approval).REFERENCES1. Franceschini, M.A., et. al. J. Appl. Physiol. 2002, 92, 372-384.2. Hueber, D.M., et. al. Phys. Med. Biol. 2001, 46, 41-62.3. Ma, H.Y., et. al. Proc. SPIE 1999, 3597, 642-9.CMDITR Review of Undergraduate Research Vol. 2 No. 1 Summer 2005 73
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The material is based upon work sup
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TABLE OF CONTENTSSynthesis of Dendr
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SYNTHESIS OF DENDRIMER BUILDING BLO
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throughout the work period. Five su
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12 CMDITR Review of Undergraduate R
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BARIUM TITANATE DOPED SOL-GEL FOR E
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BARIUM TITANATE DOPED SOL-GEL FOR E
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SYNTHESIS OF NORBORNENE MONOMER OF
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20 CMDITR Review of Undergraduate R
Page 23 and 24: using different reaction conditions
Page 25 and 26: Synthesis of Nonlinear Optical-Acti
Page 27 and 28: quality of the XRD structures wasca
Page 29 and 30: Behavioral Properties of Colloidal
Page 32 and 33: Transmission electron microscopy ha
Page 34 and 35: 34 CMDITR Review of Undergraduate R
Page 36 and 37: areorient themselves with the elect
Page 38 and 39: Fabry-Perot modulators with electro
Page 42 and 43: QUANTIZED HAMILTON DYNAMICS APPLIED
Page 46 and 47: INVESTIGATING NEW CLADDING AND CORE
Page 48 and 49: Dr. Robert NorwoodChris DeRoseAmir
Page 50 and 51: SYNTHESIS OF TPD-BASED COMPOUNDS FO
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Page 54 and 55: OPTIMIZING HYBRID WAVEGUIDESpropaga
Page 56 and 57: At closer spaces the second undesir
Page 58 and 59: SYNTHESIS AND ANALYSIS OF THIOL-STA
Page 62 and 63: QUINOXALINE-CONTAINING POLYFLUORENE
Page 64 and 65: QUINOXALINE-CONTAINING POLYFLUORENE
Page 68 and 69: SYNTHESIS OF DENDRON-FUNCTIONALIZED
Page 78 and 79: TOWARD MOLECULAR RESOLUTION C-AFM W
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Page 82 and 83: SYNTHESIS AND CHARACTERIZATION OF E
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Page 86 and 87: 1,1-DIPHENYL-2,3,4,5-TETRAKIS(9,9-D
Page 88 and 89: 1,1-DIPHENYL-2,3,4,5-TETRAKIS(9,9-D
Page 90 and 91: EFFECTS OF SURFACE CHEMISTRY ON CAD
Page 92 and 93: EFFECTS OF SURFACE CHEMISTRY ON CAD
Page 96 and 97: SYNTHESIS OF A POLYENE EO CHROMOPHO
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Page 104 and 105: CHARACTERIZATION OF THE MOLECULAR P
Page 108 and 109: OPTIMIZATION OF SEMICONDUCTOR NANOP
Page 110 and 111: OPTIMIZATION OF SEMICONDUCTOR NANOP
Page 112 and 113: CHARACTERIZATION OF THE PHOTODECOMP
Page 116 and 117: ELECTROLUMINESCENT PROPERTIES OF OR
Page 120 and 121: DETERMINATION OF MOLECULAR ORIENTAT
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DETERMINATION OF MOLECULAR ORIENTAT
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HYDROGEL MATERIALS FOR TWO-PHOTON M
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HYDROGEL MATERIALS FOR TWO-PHOTON M
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THE DESIGN OF A FLUID DELIVERY SYST
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THE DESIGN OF A FLUID DELIVERY SYST
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Student Project Abstracts 2005 - Pluto - University of Washington

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